Nitrocellulose base propellant coated with graphite,plasticizer,and inorganic pigment



United States Patent NITROCELLULOSE BASE PROPELLANT COATED WITHGRAPHITE, PLASTICIZER, AND INOR- GANIC PIGMENT Hermann Herzog, deceased,late of Kaufbeuren, Germany, by Johanna Herzog, heir, Kaufbeuren, andHubert Frey, Steyerberg, Germany, assignors to Dynamit NobelAktiengesellschaft, Troisdorf, Germany No Drawing. Filed Dec. 1, 1967,Ser. No. 689,746

Int. Cl. C06b 19/02 US. Cl. 149-11 16 Claims ABSTRACT OF THE DISCLOSUREThe present disclosure relates a a propellant charge powder having anitrocellulose base wherein the grains of the powder are coated with aplasticizer, graphite, and at least one inorganic pigment. Particularadvantages are gained with an inorganic pigment from the groupconsisting of metal oxides and metal sulfides, with specificallyadvantageous examples being iron oxide, molybdenum sulfide, titaniumdioxide, or zinc oxide, within the range of 0.1 to 1.0 percent by weightof the charge.

When a particularly high effectiveness is required for a propellantcharge powder, nitrocellulose base propellant charge powder isconventionally manufactured in the form of a loose powder. In thiscondition, it is necessary to treat the loose powder with a plasticizer,for example, dibutylphthalate, or another coating agent, for example,symmetrical diethyldiphenylurea, in such a manner that the outermostlayer of the powder granules is impregnated by this plasticizer orcoating substance. This treatment, called stabilization, will slow downthe initial combustion of the powder to a predetermined degree andconsequently influence the progression of powder combustion. Also, thistreatment, with the addition of a polishing agent, will advantageouslysmooth the surface of the powder granules so that a higher cubic weight,that is density, is obtained. Also, the calorific content of the powdermay be advantageously reduced.

The above-mentioned powder treatment is usually conducted in a steepangle or vertical drum, with the treating substance dissolved in anorganic solvent, such as ethyl alcohol, which does not dissolve thenitrocellulose. The solvent is applied to the powder simultaneously withthe addition of graphite so that the powder will have a smoothlypolished surface when the treatment is terminated.

However, experience has shown that the above-described treatment mayunder certain circumstances cause an undesirable and intolerable delayin the firing of the powder. The delay in firing increases with theamount of stabilizer added; the delay in firing being defined as thetime from the instant of firing the primer composition to the actualfiring of the powder. A too long delay in firing time must be avoided atall cost. This disadvantage of the prior art is more apparent thesmaller the ratio of surface to mass of the powder granule.

An additional disadvantage occurring during the abovementioned treatmentis that the graphite may form nodules to produce a non-uniform andunsatisfactory product, because of the poor wettability of the graphite.

It is known to overcome the firing delay disadvantage by adding groundaluminum or magnesium powder during the treatment, because theseadditives have the effect of imparting to the stabilized surfaces of thepowder granules a greater ignition tendency. To further this sensitivityeffect, it is also known to add saltpeter or other oxygen-evolvingsubstances to the powder during the treatment thereof.

3,506,505 Patented Apr. 14, 1970 Also, it is necessary to remove theresidues of the solvent after the stabilizing treatment with a watertreatment of the stabilizer-treated loose powders at high temperatures.However, the sensitivity of aluminum or magnesium to water has a verydisadvantageous effect upon the stability of the powder, while theaddition of saltpeter or other oxygen evolving water soluble salts iscompletely out of the question because of the subsequent watertreatment. Therefore, solutions by the addition of ground aluminum ormagnesium powder and the addition of saltpeter or similarly effectivesubstances has proven to be unsatisfactory.

It is an object of the present invention to avoid the above-mentioneddisadvantages. The present invention employs particular additives toprevent the formation of graphite nodules during the powder treatment,to increase the ignition sensitivity that would otherwise be reduced bythe addition of a stabilizer and provide for the subsequent waterremoval of solvent residues without adversely affecting the treatedpowder.

According to the present invention, inorganic pigments, particularlymetallic oxides and metallic sulfides are added during the surfacetreatment of the powder with a stabilizing agent. Particularlyadvantageous results have been obtained with inorganic pigments such asiron oxide (ferric oxide or ferrous oxide), molybdenum sulfide, titaniumdioxide, zinc oxide, iron sulfide, or zinc sulfide, in an amountcorresponding to desired degree of ignition sensitivity, preferablybetween 0.1 and 1.0 percent by weight of the charge.

The above noted substances added according to the present invention areknown by the commercial names of polishing rouge, Molykote, titaniumwhite (titania), and zinc white. These substances are particularlysuitable because they are excellent polishing agents due to their goodwettability and moreover increase, in mixture with graphite, theignition tendency of the powder, which would otherwise be decreased bythe stabilizer addition. With such an increase in the ignition tendency,the period from the ignition of the primer to the actual initial firingof the powder may be adapted to the particular requirements. Also, thesubstances added by the present invention reduce the moisturesensitivity of the resulting powder in an advantageous manner.

The resulting propellant powder may be used in a cartridge case forpropelling a projectile out of the barrel of a weapon, or as apropellant in a rocket.

Although it is known to add the known treating agents, includinggraphite in a batch-wise manner, it is a particular feature of thepresent invention to add the inorganic additives of the presentinvention in a batch-wise manner to the nitrocellulose base powder toobtain as uniform a distribution of the additives in the powder aspossible.

The advantages of the present invention in adding the abovementionedmineral or inorganic additives to the nitrocellulose base powder can beseen, for example, from the fact that a nitrocellulose-7-hole powdertreated with 4% camphor and 0.2% graphite on its surface attained aballistic velocity of 1.151 milliseconds at a gas pressure of 2929atmospheres and a firing development period of 2.9 milliseconds, whereaswhen using nitrocellulose-7* hole powder surface treated with 4%camphor, 0.1% graphite, and 1.0% titanium white, there was attained aballistic velocity of 1,167 milliseconds at a gas pressure of 3102atmospheres and with a firing development period of only 1.9milliseconds. The above test brings out the advantages of the presentinvention by comparing the known surface treatment of a specific powderwith the surface treatment according to the present invention of thesame specific powder. The expression 7-hole powder mentioned aboverefers to granulate powder in cylinder form which is provided with 7holes or bores extending in the longitudinal direction and distributedsymmetrically over the cross section of said cylinder for the purpose ofincreasing the burning surfaces of the powder.

As was demonstrated by additional tests, a substantial improvement isstill achieved even when a lesser amount of titanium white is used.

The lowering of the moisture sensitivity of the powder due to theaddition of the mineral additives according to the present invention canbe seen from the fact that when a nitrocellulose-7-hole powder is storedat a relative atmospheric humidity of, for example, 35 and 91%, whichpowder was surface-treated with 6% camphor and 0.2% graphite, there isalso a difference in the H content of 1.0%, whereas the samenitrocellulose-7-hole powder when treated with 6% camphor, 0.1%graphite, and 1.0% titanium white, at a difference in H O of only 0.94%.The above test comparing the moisture sensitivity of a specific powdertreated according to the known treatments and the moisture sensitivityof the same powder treated according to the present invention bring outthe advantages of the present invention in this regard.

The specific and highly advantageous results have been obtained with theadditives iron oxide, molybdenum sulfide, titanium dioxide, or zincoxide when within the range of 0.1 to 1.0% by weight of the charge.

The foregoing specific embodiments have been described in detail alongwith their specific advantages as preferred embodiments of the broaderinvention, and further modifications, embodiments and variations of thepresent invention are contemplated within the spirit and scope of theinvention as defined by the following claims.

We claim:

1. A process for influencing the ignition sensitivity of anitrocellulose base propellant charge powder which comprises coating thesurfaces of the propellant powder with a plasticizer, graphite and aninorganic pigment selected from the group consisting of metallic oxidesand metallic sulfides, said inorganic pigment being added in an amountsufficient to achieve the desired degree of firing sensitivity.

2. The process of claim 1, wherein the inorganic pigment is added in anamount of about 0.1 to 1.0% by Weight of the charge.

3. The process of claim 1, wherein the inorganic pigment is selectedfrom the group consisting of ferrous oxide, ferric oxide, titaniumdioxide, zinc oxide, molybdenum sulfide, iron sulfide and zinc sulfide.

4. A process for increasing the ignitability of a propellant chargepowder consisting essentially of nitrocellulose which comprises coatingthe surfaces of the propellant powder with a mixture of a plasticizer,graphite and an inorganic pigment selected from the group consisting ofmetallic oxides and metallic sulfides, said inorganic pigment beingadded in an amount of about 0.1 to 1.0% by weight of the charge.

5. The process of claim 4, wherein the coating step increases theconcentration of flammable substances on the surface of the propellantpowder.

6. The process of claim 4, wherein the inorganic pigspectively.

9. The process of claim 1, wherein the coating step includes adding theplasticizer, graphite and inorganic pigment by batch-wise addition.

10. A propellant charge consisting essentially of a nitrocellulose basepropellant charge powder coated with a plasticizer, graphite and aninorganic pigment selected from the group consisting of metallic oxidesand metallic sulfides, said inorganic pigment being present in an amountsufiicient to achieve the desired degree of firing sensitivity.

11. The propellant charge of claim 10, wherein the inOrganic pigment ispresent in an amount of about 0.1 to 1.0% by weight of the charge.

12. The propellant charge of claim 10, wherein the inorganic pigment isselected from the group consisting of ferrous oxide, ferric oxide,titanium dioxide, Zinc oxide, molybdenum sulfide, iron sulfide and zincsulfide.

13. A propellant charge with increased ignitability which consistsessentially of nitrocellulose powder coated with a mixture of aplasticizer, graphite, and an inorganic pigment selected from the groupconsisting of metallic oxides and metallic sulfides, said inorganicpigment being present in an amount of about 0.1 to 1.0% by weight of thecharge.

14. The propellant charge of claim 13, wherein the inorganic pigment isselected from the group consisting of iron oxide, titanium dioxide, zincoxide and molybdenum sulfide.

.15. The propellant charge of claim 13, wherein the propellant charge isnitrocellulose powder and the plasticizer is camphor.

16. The propellant of claim 15, wherein the camphor and graphite arepresent in amount of about 4% and about 0.1%, respectively.

References Cited UNITED STATES PATENTS 692,143 1/1902 Jones 1499 693,5472/1902 Jones 1499 1,354,442 9/1920 Woodbridge et a1 149-9 1,390,7409/1921 Woodbridge 1499 1,393,623 10/1921 Henning 1499 2,131,354 9/1938Marsh 149--9 2,865,729 12/1958 Foster et al 149-9 CARL D. QUARFORTH,Primary Examiner S. J. LECHERT. JR., Assistant Examiner US. Cl. X.R.149-9, 10,

